Conventionally, a terminal (hereinafter referred to as a “network management terminal”) of a network management system (NMS) is connected to a network constituted by a plurality of network elements (NE), so as to control and manage cross-connects.
FIG. 1 is a system block diagram for explaining the NMS. In FIG. 1, a plurality of network elements 10a through 10e, such as switching equipments and network elements, are connected to constitute a network 12 such as a telecommunication network. Each of the network elements 10a through 10e is connected to a data communication network 14 such as a telecommunication management network (TMN). Network management terminals 16a through 16c and a maintenance terminal (workstation) 18 which is used as a kind of the network management terminal are connected to the data communication network 14.
FIG. 2 is a system block diagram of an example of a network including the NMS. In FIG. 2, the network has a structure such that high-speed network elements 20a through 20d having a transmission rate of 2.5 Gbps, for example, are connected in a ring by optical fiber transmission channels 21a through 21d. In addition, a medium-speed optical network element 20f having a transmission rate of 600 Mbps is connected to the network element 20b via an optical fiber transmission channel 21e, and a low-speed optical network element 20g having a transmission rate of 150 Mbps is connected to the network element 20c via an optical fiber transmission channel 21f. The transmission rate of 2.5 Gbps has a capacity to pass sixteen VC4 (Virtual Container 4) signals at 140 Mbps according to the ITU-T recommendations. The transmission rate of 600 Mbps can pass four VC4 signals, and the transmission rate of 150 Mbps can pass one VC4 signal. Accordingly, each of the network elements 20a through 20d sets a cross-connect so as to form a path for the VC4 signal.
For example, the network element 20a is provided in Osaka, and the network element 20c is provided in Tokyo. A maintenance terminal 22 and a network management terminal (NMS#1) 24 are connected to the network element 20a in Osaka. A network management terminal (NMS#2) 26 is connected to the network element 20c in Tokyo. Further, a network management terminal (NMS#3) 28 is connected to the network management terminal 26. In this case, the network management terminal 28 performs an operation by referring to a database of the network management terminal 26. In addition, as shown in FIG. 30, for example, in a network where the network elements 20a through 20d are connected in a ring, network elements 20g through 20j are connected in a ring, and the network elements 20c and 20g are connected, when network management apparatuses 24 and 25 are connected to the network elements 20b and 20i, respectively, and a network management terminal 27 is connected to the network management terminals 24 and 25, the network management terminal 27 centrally manages information (alarm information and cross-connect information) of the network management terminals 24 and 25, and issues an instruction to the network management terminals 24 and 25 so as to transmit commands.
In FIG. 2, the maintenance terminal 22 can be connected to a network element the maintenance terminal 22 intends to perform maintenance, and can set a cross-connect only with respect to this network element. On the other hand, the network management terminals 24, 26 and 28 can form a path from an arbitrary point in a network to another arbitrary point in the network via a plurality of network elements which are not limited to the network elements connected to the network management terminals 24, 26 and 28. For example, the network management terminals 24, 26 and 28 can form a path for the VC4 signal via the four network elements 20f, 20b, 20c and 20g. In this case, the network management terminals 24, 26 and 28 set cross-connects at each of the network elements 20f, 20b, 20c and 20g. 
Conventionally, it is possible to set/cancel a cross-connect of an arbitrary network element from any network management terminal or maintenance terminal, as long as an NE user ID which is input to the network management terminal or maintenance terminal when operating a network element is equal to or higher than a predetermined security level, and at the same time, an NMS user ID has an authority to operate a cross-connect function.
For this reason, in a case where tests such as an operation check and a communication error check of a network element are conducted in parallel with an actual operation, there is a problem in that a signal used in the actual operation is erroneously cut off when a cross-connect of a testing network element is set/canceled from an arbitrary network management terminal.